The present invention relates to a laser oscillation device using a semiconductor laser as a pump source.
As a laser oscillation device which is used for a spectroscopic measurement, a shape gauging IJ, a nonlinear crystal pump, and others, there is, for instance, a Q switch laser device using an isotropic laser medium such as Nd:YAG. The Q switch laser device comprises a light emitting unit for emitting a laser light with a predetermined wavelength and an optical resonator. The optical resonator comprises a first dielectric reflector, a second dielectric reflector, a laser crystal and a saturable absorber arranged between the first dielectric reflector and the second dielectric reflector.
In the Q switch laser device, a laser crystal is pumped by a pumped laser beam emitted from the light emitting unit, and a spontaneous emission light emitted from the laser crystal is absorbed by the saturable absorber. With the absorption of the spontaneous emission light, an electron density on a pump level of the saturable absorber gradually increases, and the saturable absorber becomes transparent when the electron density is saturated. When the saturable absorber becomes transparent, a laser oscillation occurs, and a pulsed light is emitted.
In case of performing a wavelength conversion of the pulsed light or a shape measurement by the pulsed light, it is desirable for a polarizing direction of the emitted pulsed lights to coincide with each other. However, the Q switch laser device has a polarization characteristic which the pulsed lights are alternately polarized in directions orthogonal to each other and emitted, and hence by providing with a polarization element in the optical resonator and the like, the polarizing direction of the pulsed light is controlled in the prior art.